Electrical clamp

ABSTRACT

A standard form of cast alluminum ground clamp is disclosed wherein the connecting means provided at the pivot point has shock absorbing properties and is comprised of a resilient sleeve surrounding the interconnecting rivet.

UIfitEd States Patent 1 Anderson [54] ELECTRICAL CLAMP [76] Inventor: Gordon S. Anderson, Daheim Road,

Millbrook, NY. 12545 [22] Filed: Sept. 27, 1971 211 App1.No.: 183,765

[52] U. S. Cl ..339/l4 R, 339/255 P, 339/261 [51] Int. Cl. .1101! 3/06 [58] Field of Search ..339/l4 R, 255 P, 339/93, 260, 261,108, 58; 267/137; 24/8135, 253; 81/415, 416, 417

[56] References Cited UNITED STATES PATENTS 3,641,473 2/1972 Attaway ..339/14 R 51 June 5,1973

3,157,770 11/1964 Beaulieu ..200/166 3,644,877 2/ 1972 Carbonneau 2,851,672 9/1958 Odenwald 2,412,492 12/1946 Brazitis ..339/261 Primary Examiner-Marvin A. Champion Assistant Examiner-Robert A. Hafer Attorney-Robert W. Berray [57] ABSTRACT A standard form of cast alluminum ground clamp is disclosed wherein the connecting means provided at the pivot point has shock absorbing properties and is comprised of a resilient sleeve surrounding the interconnecting rivet.

6 Claims, 3 Drawing Figures Patented June 5, 1973 3,737,832

FIG.2

FIG.3

l i iulii, 26 "18 k/ZS I. n H

. Q gs?) I iNVENTOR GORDON S ANDERSON ELECTRICAL CLAMP FIELD OF THE INVENTION This invention relates to clamps, and more particularly to clamps requiring a large force to operate.

BACKGROUND OF THE INVENTION Prior ground clamps have been constructed of cast aluminum for the purpose of connecting military vehicles to a ground rod which normally has a diameter of approximately it of an inch. Specifications require that the force required to open the cooperating jaws for application to the ground rod should be approximately 40 pounds. It has become common practice for personnel using the ground clamp to remove the clamp from the ground rod by merely pulling on the connecting cable or one of the handles rather than squeezing the handles SUMMARY OF THE INVENTION The present invention has discovered that breakage previously encountered can be eliminated by providing shock absorbing material around the interconnecting rivet at the pivot point of the clamp. In a preferred embodiment of the invention, where both the upper and lower handle members of the clamp are of channel configuration, the shock absorbing member is comprised of an inner sleeve of resilient plastic and an outer metallic sleeve.

THE DRAWING In the drawings: FIG. 1 shows the overall construction of an electrical clamp incorporating the present invention.

FIG. 2 is a cross section taken through the pivot point of the electrical clamp shown in FIG. 1.

FIG. 3 shows a modification of the shock absorbing means provided by the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 will both be referred to in describing the preferred embodiment of the present invention. A prior, extensively used felectrical ground clamp includes a lower handle member 10 with a jaw portion 1 l at one end thereof, andan upper handle member 12 having a jaw member 13 which cooperates with the jaw member 11. The clamp is used to connect equipment to be grounded to a ground rod which normally has a diameter of approximately 14 of an inch. The jaw members 11 and 13 are provided with hardened steel, toothed portions for providing a biting action for positive electrical contact with the ground rod. Both members l0 and 12 are of cast aluminum and have a channel configuration as depicted in the cut out portion of handle 12.

The upper handle 12 includes, on opposite side walls, integral parallel ears 14. The lower handle 10 also is of a channel configuration and includes on, opposite side walls, integral parallel ears 15. Aligned transverse holes in the parallel ears define a pivot point 16. The transverse dimension of the upper handle 12 is such that the parallel ears 14 are positioned on the outside of the parallel ears 15.

In the prior electrical clamp, the holes in the parallel ears l4 and 15, which define the pivot point 16, have the same size. A rivet l7 interconnects the handles 10 and 12 at the pivot point. Spring tension for the clamp is provided by a torsion spring 18 having its convolutions 19 centered about, and surrounding the rivet 17.

The ground clamp is connected to any apparatus to be grounded by a cable 20 fastened to the clamp by set screws 21. The electrical path provided to cable 20 for static electricity having high voltage, low current can be jaw tip 13 and handle 12, or jaw tip 11, handle 10, spring 18 and handle 12. As indicated earlier, normal practice for removing the clamp from the ground rod was to pull on the cable 20 which thereby forced the tips of the jaw members 11 and 13 to come together with such force that breakage was occurring at points 22 or 23.

In accordance with the present invention, the shock created when the tips of the jaw members 11 and 13 come together can be absorbed by providing a shock absorber at the pivot point 16. The only modification required to the basic clamp configuration previously described is to enlarge the diameter of the ,holes through the parallel ears 15 of the lower handle member 10. The holes in the parallel ears 15 are enlarged to accommodate a shock absorbing sleeve member 24 I surrounding the rivet 17. In the preferred embodiment of the present invention the sleeve member 24 is comprised of an inner resilient sleeve comprised of cast, unfilled polyurethane having a durometer, or resiliency reading, of 88. The material utilized in the preferred embodiment of the present invention is known as imfilled adaprene manufactured by DuPontCorporation. For reasons to be discussed subsequently, the shock absorbing sleeve member 24 is also comprised of an outer sleeve comprised of a ductile, half-hard brass tube 26.

In order to provide desirable shock absorbing properties, the inner sleeve 25 must exhibit a sufficient amount of resiliency. It is noted in FIG. 2 that the outer diameter of the inner sleeve 25 is greater than the diameter of the hole through the parallel ears 14. In the construction shown, the ends of the sleeve 25 are shown to be flush with the outer surface of the parallel cars 15 and against the inner surface of the parallel ears 14. At the instant of maximum pressure on the inner sleeve 25, the inner sleeve 25 is prevented from being deformed in the transverse direction by the walls of the parallel ears l4.

In the absence of the outer sleeve member 26, the inner resilient sleeve 25 would be deformed in a radial direction between the parallel ears 15. By confining the inner resilient sleeve 25 by means of the outer metallic sleeve 26, and the inner surface of the parallel ears l4, stresses which would normally rupture the resilient inner sleeve 25 are prevented, thus, extending the life of the shock absorbing resilient sleeve 25.

A desirable feature realized by the construction of the preferred embodiment of the present invention is a creeping effect that takes place in the combination. That is, each use of the clamp includes two cycles of rotation about the pivot pin 16. The first cycle includes a rather slow speed rotation when applying the clamp to a ground rod. When the clamp is removed from the ground rod by pulling it free by the cable 20, high speed rotation about the pivot point 16 occurs. This combined effect of low and high speed rotation about the pivot point 16 causes the shock absorbing sleeve member 24 to rotate about the rivet 17 to thereby distribute the wear on the shock absorbing sleeve member 24. This also extends the life of the shock absorbing sleeve member 24.

FIG. 3 represents a modification of the clamp construction eliminating the need for the outer metallic sleeve member 26. If the spring tension provided for the clamp is by means of a coil or leaf spring extending outward pressure at 27 on the upper and lower members, the lower handle member need not be of a channel configuration and would merely be provided with an upward extending projection 28 with a transverse hole at the pivot point 16. The upper handle member 12 would still be of a channel configuration having parallel ears 14 extending outside of the projection 28. It is clear, therefore, that the shock absorbing sleeve member 24 need only include the shock absorbing resilient sleeve 25. The shock absorbing sleeve 25 will be confined by the solid construction of the projection 28. Therefore, the outer metallic sleeve 26 of FIG. 2 is not required.

As shown in FIG, 1, additional shock absorbing properties are achieved by providing, as an integral part of jaw members 11 and 13, anvil shaped striking areas 29 and 30. This has the effect of preventing the tips of jaw members 11 and 13 from coming together when the clamp is pulled from the ground rod. Therefore, the area of the jaw members 11 and 13 which must absorb the impact forces is moved closer to the shock absorbing sleeve member 25.

While I have illustrated and described preferred embodiments of my invention, it is understood that these are capable of modification, and I therefore do not wish to be limited to the precise detail set forth but desire to avail myself of such changes and alterations which fall within the pervue of the following claims.

I claim:

1. An electrical clamp comprising:

a lower member having at one end thereof a jaw porone end thereof a jaw portion for cooperating with the jaw portion of said lower member, and intermediate its ends on opposite side walls thereof integral parallel ears with aligned holes defining a pivot point, said parallel ears extending along the outside,

surfaces of said lower member; tension means cooperating with said upper and lower member for urging said jaw portions together about said pivot point; and means connecting said upper member to said lower member at said pivot point, said means surrounded by a resilient sleeve member which extends at least to the said outside surfaces of said lower member. 4

2. An electrical clamp in accordance with claim 1 wherein:

said sleeve member has an outside diameter greater than the diameter of said aligned holes, and a length equal to the distance between the outside surfaces of said lower member. .3. An electrical clamp in accordance with claim 2 wherein:

said lower member is of channel configuration and has intermediate its ends on opposite side walls thereof integral parallel ears with aligned holes at said pivot point; and said sleeve member includes,

an inner sleeve of resilient plastic, and an outer metallic sleeve. 4. An electrical clamp in accordance with claim 3 wherein:

said tension means is a torsion spring, the convolutions thereof being positioned around said sleeve member, and the ends thereof being in engagement with said upper and lower members. 5. An electrical clamp in accordance with claim 4 wherein:

said inner sleeve is comprised of cast, unfilled polyurethane having a durometer reading of approximately 88; and. said outer sleeve is comprised of ductile, half-hard brass. 6. An electrical clamp in accordance with claim 1 wherein:

each of said jaw portions includes, intermediate the tips and said pivot point; integral projections providing a striking area and adapted to prevent contact between the tips of said jaw portions.

Ii i l 

1. An electrical clamp comprising: a lower member having at one end thereof a jaw portion; an upper member of channel configuration having at one end thereof a jaw portion for cooperating with the jaw portion of said lower member, and intermediate it''s ends on opposite side walls thereof integral parallel ears with aligned holes defining a pivot point, said parallel ears extending along the outside surfaces of said lower member; tension means cooperating with said upper and lower member for urging said jaw portions together about said pivot point; and means connecting said upper member to said lower member at said pivot point, said means surrounded by a resilient sleeve member which extends at least to the said outside surfaces of said lower member.
 2. An electrical clamp in accordance with claim 1 wherein: said sleeve member has an outside diameter greater than the diameter of said aligned holes, and a length equal to the distance between the outside surfaces of said lower member.
 3. An electrical clamp in accordance with claim 2 wherein: said lower member is of channel configuration and has intermediate its ends on opposite side walls thereof integral parallel ears with aligned holes at said pivot point; and said sleeve member includes, an inner sleeve of resilient plastic, and an outer metallic sleeve.
 4. An electrical clamp in accordance with claim 3 wherein: said tension means is a torsion spring, the convolutions thereof being positioned around said sleeve member, and the ends thereof being in engagement with said upper and lower members.
 5. An electrical clamp in accordance with claim 4 wherein: said inner sleeve is comprised of cast, unfilled polyurethane having a durometer reading of approximately 88; and said outer sleeve is comprised of ductile, half-hard brass.
 6. An electrical clamp in accordance with claim 1 wherein: each of said jaw portions includes, intermediate the tips and said pivot point; integral projections providing a striking area and adapted to prevent contact between the tips of said jaw portions. 